CO.sub.2 lasers which were originally used in dermatological applications, emit a continuous beam having a wavelength of about 10,600 nm, in the mid-infrared portion of the electromagnetic spectrum. Laser energy is absorbed by biological tissue regardless of its pigmentation, due to the fact that the target of the beam is water which is the main component of the skin. The CO.sub.2 laser destroys tissue by rapidly heating and vaporizing intracellular water. The conventional CO.sub.2 laser also causes a large buildup of heat in the surrounding tissue as heat is conducted away from the irradiated site and thus the damage is not confined solely to that target site.
A newer development has been the use of the so called "resurfacing" CO.sub.2 lasers which are used by dermatologists for the ablation of skin tissue generally for cosmetic purposes. The resurfacing CO.sub.2 lasers deliver energy in much shorter bursts and within shorter periods of time, so that the heat conduction from the site of irradiation is substantially minimized. The resurfacing laser modifies the delivery of energy so that heat will not accumulate on, or conduct through to adjacent tissue, therefore, the lateral thermal damage is decreased. The water is rapidly vaporized from cellular tissues as an effect of the laser energy which creates a localized wound in somewhat of an "explosive" fashion, resulting in a skin condition similar to third degree burns. Each pass of the laser ablates approximately 50 to 100 .mu.m of tissue. Complete ablation of tissue requires sufficient energy to vaporize the water contained in the tissue. If a sufficiently quick vaporization takes place, there is not enough time for an appreciable amount of heat conduction into surrounding tissue to cause thermal damage, but the delivered power density is sufficient to accelerate the rate of vaporization over the rate of heat conduction. Thus the ablation front travels faster than the thermal conduction front, resulting in somewhat less of a thermal injury, than with conventional CO.sub.2 lasers.
Nevertheless, even the improved resurfacing laser technique results in a substantial inflammation of the skin with pronounced erythema, and in pronounced drying resulting in scaling and flaking of the skin, as well as a darkening of the skin due to the development of dark melanin pigmentation.
The dry, flaky and irritated skin which is the result of the moisture loss and of associated chemical insults, is due to biochemical and morphological changes in the stratum comeum of the dry skin. Much of the deterioration was found to be occasioned by the degradation of desmosomes in the lower layers of the stratum comeum, because they were found to rise to the surface during the laser attack, while being abnormally retained in the xerotic stratum comeum. Therefore, it was concluded that for the inter-corneocyte cohesion is broken down desquamation which produces post-laser, and resulting in the degradation of the desmosomes by enzymes during the desquamation.